Accelerational Implications of Hummingbird Display Dives

Integrative Biolog

Filling in the retinal image

The optics of the eye form an image on a surface at the back of the eyeball called the retina. The retina contains the photoreceptors that sample the image and convert it into a neural signal. The spacing of the photoreceptors in the retina is not uniform and varies with retinal locus. The central retinal field, called the macula, is densely packed with photoreceptors. The packing density falls off rapidly as a function of retinal eccentricity with respect to the macular region and there are regions in which there are no photoreceptors at all. The retinal regions without photoreceptors are called blind spots or scotomas. The neural transformations which convert retinal image signals into percepts fills in the gaps and regularizes the inhomogeneities of the retinal photoreceptor sampling mosaic. The filling-in mechamism plays an important role in understanding visual performance. The filling-in mechanism is not well understood. A systematic collaborative research program at the Ames Research Center and SRI in Menlo Park, California, was designed to explore this mechanism. It was shown that the perceived fields which are in fact different from the image on the retina due to filling-in, control some aspects of performance and not others. Researchers have linked these mechanisms to putative mechanisms of color coding and color constancy

A3I visibility modeling project

The Army-NASA Aircrew Aircraft Integration program is supporting a joint project to build a visibility computer-aided design (CAD) tool. CAD has become an essential tool in modern engineering applications. CAD tools are used to create engineering drawings and to evaluate potential designs before they are physically realized. The visibility CAD tool will provide the design engineer with a tool to aid in the location and specification of windows, displays, and control in crewstations. In an aircraft cockpit the location of instruments and the emissive and reflective characteristics of the surfaces must be determined to assure adequate aircrew performance. The visibility CAD tool will allow the designer to ask and answer many of these questions in the context of a three-dimensional graphical representation of the cockpit. The graphic representation of the cockpit is a geometrically valid model of the cockpit design. A graphic model of a pilot, called the pilot manikin, can be placed naturalistically in the cockpit model. The visibility tool has the capability of mapping the cockpit surfaces and other objects modeled in this graphic design space onto the simulated pilot's retinas for a given visual fixation

Does Colour Filling-In Account for Colour Perception in Natural Images?

It is popular to attribute the appearance of extended colour fields to a process of filling-in from the differential colour signals at colour edges, where one colour transitions to another. We ask whether such a process can account for the appearance of extended colour fields in natural images. Some form of colour filling-in must underlie the equiluminant colour Craik-O’Brien-Cornsweet effect and the Water colour Effect, but these effects are too weak to account for the appearance of extended colour fields in natural images. Moreover, the graded colour disappearance effect reported as evidence for colour filling-in does not work under natural viewing conditions. We demonstrate that natural images do not look very colourful when their colour is restricted to edge transitions . Moreover, purely chromatic images with maximally graded (‘edgeless’) transitions look fully colourful. Consequently, we conclude that colour filling-in makes no more than a minor contribution to the appearance of extended colour regions in natural images

Public rules about using and owning real estate in Cuba

The discussion on urban land continues to be absent in most of the specialized Cuban literature about planning and economic policies, despite its relevance. In very thorough essays about the present challenges and future development of the Cuban economy, nothing is said about the need for adequate public land policies and the implementation of public value capture mechanisms as part of the economic development of the country. The issue is complex, there is a void of almost half a century of not dealing with land value, but these reasons are not sufficient to justify the continued lack of vision in this direction, all the more when the Cuban cities are in desperate need to reverse the deterioration and stagnation that affects them. The Cuban state determines the general rules under which citizens and organisations may own and use real estate. These are rules about property rights and about the limitations - in compliance with aspects such as state security, environmental and heritage protection, economic development, social equity and human and civil rights – on exercising those rights. In doing this, the Cuban state is no different from other states: most states make such rules and enforce them when necessary. What is particular to Cuba is the content of those rules. In particular, the Cuban state has the monopoly to perform land development and management. There are public institutions to plan and deal with all of these aspects, and there are no recognised real estate markets in the country. Another important aspect is the utmost importance given to planning. But in spite of this, Cuban urban planners have rarely been certain of what will be built and where. The main reason for this may be that, despite the numerous master plans to study and anticipate development trends, most of the decisions ultimately involve top officials who envision the projects and establish the investment priorities according to the public interests or needs and the historical moment, irrespective of the plans. This article intends to give a clear picture of how things are done in the public sector, how the administration works, and under which legal framework. I will look at the physical planning system and its importance in the location and implementation of land use, investment projects and housing programs, and at the legal procedures that include licenses for construction, demolition, habitat and other licenses for heritage conservation and redevelopment. I will analyze the difficulties faced by the Cuban planning and legal system with respect to land and urban development, in the attempt to understand the limits imposed by the government on land and urban development, and I will explore to what extent those limits are to blame for the increasing irregularities and violations at all levels of the formal procedures for land and property. I will also introduce the public and personal rights concerning housing, buying and selling, permutes, donations and other tenure alternatives; and clarify the civil responsibilities, namely types of ownership, properties, property registers and so forth in order to expose the opportunities and accessibility of the system but also its limitations

Making the Earth: Combining Dynamics and Chemistry in the Solar System

No terrestrial planet formation simulation completed to date has considered the detailed chemical composition of the planets produced. While many have considered possible water contents and late veneer compositions, none have examined the bulk elemental abundances of the planets produced as an important check of formation models. Here we report on the first study of this type. Bulk elemental abundances based on disk equilibrium studies have been determined for the simulated terrestrial planets of O'Brien et al. (2006). These abundances are in excellent agreement with observed planetary values, indicating that the models of O'Brien et al. (2006) are successfully producing planets comparable to those of the Solar System in terms of both their dynamical and chemical properties. Significant amounts of water are accreted in the present simulations, implying that the terrestrial planets form "wet" and do not need significant water delivery from other sources. Under the assumption of equilibrium controlled chemistry, the biogenic species N and C still need to be delivered to the Earth as they are not accreted in significant proportions during the formation process. Negligible solar photospheric pollution is produced by the planetary formation process. Assuming similar levels of pollution in other planetary systems, this in turn implies that the high metallicity trend observed in extrasolar planetary systems is in fact primordial.Comment: 61 pages (including online material), 12 figures (7 in paper, 5 online). Accepted to Icaru

Illicit substance use among university students from seven European countries: A comparison of personal and perceived peer use and attitudes towards illicit substance use

Objective: To compare European students' personal use and approval of illicit substance use with their perceptions of peer behaviours and attitudes, and investigate whether perceptions of peer norms are associated with personal use of illicit substances and attitudes. Method: This study used baseline data fromthe Social Norms Intervention for the prevention of Polydrug usE (SNIPE) project involving 4482 students from seven European countries in 2012. Students completed an online surveywhich included questions on personal and perceived peer illicit substance use and personal and perceived peer attitude towards illicit substances. Results: 8.3% of students reported having used illicit substances at least once in their life. 49.7% of students perceived that the majority of their peers have used illicit substances more frequently than themselves. The perception was significantly associated with higher odds for personal illicit substance use (OR: 1.97, 95% CI: 1.53–2.54). The perception that the majority of peers approve illicit substance use was significantly associated with higher odds for personal approval of illicit substance use (OR: 3.47, 95% CI: 2.73–4.41). Conclusion: Students commonly perceived that their peers used illicit subtances more often than themselves. We found an association between the perceived peer norms/attitudes and reported individual behaviour/ attitudes

The Impact of Community Schools on Education Outcomes in Knox County Schools

This thesis seeks to isolate the effect of community schools on the education outcomes of students participating in the program as well as the added benefit to the community. It relies on OLS regression with state-based standardized testing results to predict the relationship of adding a community school program in Knox County. Furthermore, the Regional Input-Output Modeling System (RIMS II) generates an estimate of the economic impact Knox County schools have on the Knox County economy. Both results, interpreted alongside personal experience, highlight the policy benefits of additional community schools in a given County. This process also highlights shortcomings of state reporting of school performance and provides suggestions for future research